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MG MGF Technical - Oversizing

Hi,
car = 96 MGF 1.8i
history :
piston failure in 1 chamber causing replacement of said piston + valves. car recently undergone general overhaul. w/shop said, cylinder wall/lining on 1 chamber is scratched/worn, options are 1)new engine 2)oversizing bore, hence requiring larger pistons. now i'm considering to do the second option.

question :
is there any other way to repair cylinder lining?
what are the advantages/disadvantages of oversizing the cylinder bore?
anyone got measurements of each stage of oversizing(how far, how big, final engine capacity)?
what parts need to be replaced?

Regards.



Dani

´
Hi Dani,
surely the piston and liner should be replaced as one set and not separated !Is it really possible to buy just a piston without mating liner ?? Also very important is liner height as this affects how well the head and gasket will seal... With such a re-build as this it may be better to get a full set of 4 pistons + liners with the correct height.
Others that have more "hands-on" experience will certainly tell more...

BR, Carl.
Carl Blom

I agree with Carl,

It would be far better and more economical to get four pistons+liners. Don't forget the uprated head gasket. Make sure it is the latest or get one yourself from Mike Satur.

Bruce
Bruce Caldwell

I would be very dubious about incressing the bore by thining the liners, haynes talk about removing the liners on the 1.4, but they are dry liners, and the 1.8 has wet liners- I don't see why it would not be possible to change them though.

Will
Will Munns

I agree with Will on this one. The 1.8 is basically a bored out 1.4 with a longer stroke. In other words, it has already been bored out. Any more out of the liners would be dangerous IMO as you will be eating into the margin of safety.

SF
Scarlet Fever

Thanks all for the input.

>It would be far better and more economical to get four pistons+liners

>>and the 1.8 has wet liners- I don't see why it would not be possible to change them though.

From the responses, I assume that these liners are some sort of sleeve to put against the chamber wall?? If so, engine will still be original specs. any part numbers for the liners?

Regards.
Dani

K series engines are alloy block with steel cylindrical liners to sleeve the pistons.

1.4 has dry liners.

1.6 has larger bore 'damp' liners.

1.8 has same liners as 1.6 but with a longer stroke.

Effectively, the 1.8 is a bored out 1.4 engine (hence small size and very good power to weight ratio).

SF
SF

Hi,
It turns out that the cylinder liner mentioned earlier is cracked. It wasn't visible when it's in position but when w/shop tried to remove the liner from engine block, it easily comes off.

How dealer didn't notice the cracked liner when they're replacing piston is beyond me.

Who's selling cylinder liners(just the liners) for 1996 MGF 1.8i and at what price?

Thanks.
Dani

This thread was discussed between 28/08/2002 and 30/08/2002

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